Back to EveryPatent.com
United States Patent |
5,004,068
|
Sase
,   et al.
|
April 2, 1991
|
Muffler
Abstract
A muffler is constructed to have a tubular perforated plate within its
cavity so as to divide the cavity into an outer resonant cavity and an
inner resonant cavity, to thereby provide two resonant frequencies. The
tubular perforated plate is formed in the shape of a funnel.
Inventors:
|
Sase; Toshitsugu (Kanagawa, JP);
Matsuda; Michiaki (Tokyo, JP);
Yanagisawa; Kiyoshi (Kanagawa, JP);
Maeda; Mitsuru (Kanagawa, JP)
|
Assignee:
|
Ebara Corporation (Tokyo, JP)
|
Appl. No.:
|
446766 |
Filed:
|
December 6, 1989 |
Foreign Application Priority Data
| Dec 06, 1988[JP] | 63-306950 |
Current U.S. Class: |
181/276; 181/272; 181/282 |
Intern'l Class: |
F01N 001/02 |
Field of Search: |
181/247-256,269,273,272,282,276
|
References Cited
U.S. Patent Documents
1638309 | Aug., 1927 | Kemble.
| |
1844105 | Feb., 1932 | Schnell | 181/252.
|
2088576 | Aug., 1987 | Compo.
| |
2185584 | Jan., 1940 | Boyce | 181/252.
|
2512155 | Jun., 1950 | Hill | 181/249.
|
3080940 | Mar., 1963 | Jobson.
| |
Foreign Patent Documents |
918597 | Feb., 1947 | FR.
| |
1441401 | May., 1966 | FR.
| |
Other References
"Acoustic Performance of Low-Aspect-Ratio Muffler", K. Yasui Lecturing
Paper (pp. 357-360), Japan Noise Control Technology Association, 9/86.
|
Primary Examiner: Fuller; Benjamin R.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
What is claimed is:
1. A muffler comprising:
a barrel having first and second side plates mounted to opposing ends
thereof to form a substantially enclosed cavity;
an inlet tube attached to said first side plate and communicating with said
substantially enclosed cavity;
an outlet tube attached to said second side plate and communicating with
said substantially enclosed cavity;
a perforated tube mounted within said substantially enclosed cavity and
having a first end connected to said first side plate in direct fluid
communication with said inlet tube and a second end connected to said
second side plate in direct fluid communication with said outlet tube,
said perforated tube having substantially a funnel shape, one of said
first and second ends of said perforated tube having an inside diameter
which is greater than or equal to an inside diameter of said inlet tube
and greater than or equal to an inside diameter of said outlet tube,
another of said first and second ends of said perforated tube having an
inside diameter which is greater than said inside diameter of said inlet
tube, greater than said inside diameter of said outlet tube and greater
than said inside diameter of said one of said first and second ends of
said perforated tube, said perforated tube dividing said substantially
enclosed cavity into an inner resonance cavity which is substantially void
of sound absorbing material and an outer resonance cavity which is
substantially void of sound absorbing material.
2. A muffler as recited in claim 1, wherein
said one of said first and second ends of said perforated tube comprises
said first end of said perforated tube.
3. A muffler as recited in claim 1, wherein
said barrel has a circular cross section.
4. A muffler as recited in claim 1, wherein
said barrel has a rectangular cross section.
Description
TECHNICAL FIELD
The present invention relates to a muffler and more particularly to a
resonant type muffler.
BACKGROUND OF THE INVENTION
In order to attenuate noise, a muffler is employed and its type is
generally classified as a sound absorbing type or a resonant type, etc. A
sound absorbing type muffler is provided with a sound absorbing material
filled within a muffler tube. Glass fiber, rock wool or mineral wool is
selected for a tube filling. However, these materials cannot be used in a
sound absorbing type muffler if pollution due to a sound absorbing
material is to be avoided.
On the other hand, in the case of a resonant type muffler, attenuation of
sound may be insufficient if the dimension of the muffler in the fluid
flowing direction is such that it restricts the length of its resonant
cavity. Also, in the conventional resonant type mufflers, attenuation can
only be effected within only a narrow frequency band due to the provision
of a single resonant cavity.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a resonant
type muffler, which can effectively attenuate sound over a wide frequency
band.
The above object is accomplished by a muffler constructed according to the
present invention. According to the present invention, a muffler is
constructed to have a tubular perforated plate within a cavity of a barrel
which is formed in the shape of a funnel and is in communication with
inlet and outlet tubes of the muffler. The tubular plate divides the
cavity into an outer resonant cavity and an inner resonant cavity so that
the muffler possesses two resonant frequencies and attenuation is effected
over a relatively wide frequency band.
Further details will be given in the detailed description of the embodiment
following the explanation of the drawings given below.
BRIEF EXPLANATION OF THE DRAWINGS
FIG. 1 schematically shows an example of a conventional muffler;
FIG. 2 is a drawing showing a longitudinal sectional view of an embodiment
according to the present invention;
FIG. 3 is a cross sectional view taken along the line X--X in FIG. 2;
FIG. 4 is a graph showing a comparison of the attenuation provided a
muffler according to the present invention and that provided by a
conventional muffler;
FIG. 5 is a cross sectional view similar to FIG. 3, but showing a different
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Before explaining the present invention, a conventional resonant type
muffler will briefly be explained referring to FIG. 1.
An example of a conventional resonant type muffler is shown in FIG. 1 and
comprises a cylindrical or square column cavity 20 and a tube 21 extending
through the cavity 20. Within the cavity 20, the tube 21 is provided with
multiple perforations 22 in the wall thereof so that the tube 21
constitutes a perforated plate within the cavity. In this type of muffler,
if a sufficient length of the muffler in the fluid flowing direction is
not present within the cavity, the surface area of the perforated plate is
small, such that the sound attenuation is insufficient. Also, in the
construction of a conventional muffler, there is only a single resonant
cavity. Thus, attenuation is limited to a narrow frequency band around the
resonant frequency.
Now, referring to FIGS. 2 and 3, a muffler according to the present
invention is shown schematically. In the drawings, numeral 7 designates an
outer barrel which in this embodiment is shown as a square column type.
However, the muffler may be in the form of a cylinder 7' (as shown in FIG.
5). A cavity is defined within the barrel 7, 7' by side plates 6, 8 and
the barrel 7, 7'. To the side plates 6 and 8, an intake tube 1 and an
outlet tube 5 are attached, respectively. Within the barrel 7, 7' a
perforated plate 2 is installed. The plate 2 is formed in a cylindrical
shape which expands from the side of the inlet tube 1 towards the side of
the outlet tube 5 in a manner resembling a funnel shape. The minimum cross
sectional area of the perforated plate 2 relative to the fluid flowing
direction is equivalent to, or more than, that of the intake tube and the
maximum cross sectional area thereof is arranged to be larger than that of
the outlet tube. It is to be noted that the direction of expansion of the
perforation plate 2 may be opposite to that shown in FIG. 2. By the
tubular perforated plate 2, the cavity of the barrel 7, 7' is divided into
an outer resonant cavity 3 and an inner resonant cavity 4.
In the muffler constructed as above, a sound wave entering from the inlet
tube 1 passes through the perforated plate 2 and propagates within the
resonant cavity 3 wherein it is attenuated by resonance in the cavity 3.
Further, the sound wave also causes resonance in the resonant cavity 4 and
is attenuated. This muffler, thus, possesses two kinds of resonant
cavities and has a resonant frequency at two points as indicated by the
curve A (solid line) in FIG. 4. In FIG. 4, the curve B (dotted line)
represents a conventional muffler which has only resonant frequency. So,
in the conventional muffler, attenuation is effected only around this one
resonant frequency. However, in the muffler according to the present
invention, attenuation is effected in a relatively wide frequency band
around the two resonant frequencies whereby attenuation is greatly
enhanced compared to attenuation provided by a conventional muffler.
Top